1. Field of the Invention
The present invention relates to a pixel circuit that exercises control over the intensity by driving, by a current, an electro-optic device provided for every pixel, an image display device in which the pixel circuit is plurally arranged in a matrix, and a drive method for the image display device. More specifically, the invention relates to an image display device of a so-called active matrix type that exercises control over the amount of current flowing to an electro-optic device, e.g., organic electroluminescent (EL) device, using an insulated gate field effect transistor (IGFET) provided to every pixel circuit, and a drive method for the image display device. The invention also relates to an electronic device equipped with such a display device.
2. Description of the Related Art
With an image display device, e.g., liquid crystal display, a plurality of liquid crystal pixels are arranged in a matrix, and the strength of transmission or reflection of an incoming light is controlled for every pixel in accordance with information about a displaying image so that the image is displayed. This is applicable also to an organic EL display or others in which pixels are electro-optic devices, such as organic EL devices, but the organic EL devices are self-light-emitting, unlike the liquid crystal pixels. Thus this allows the organic EL display to have the advantages of better image visibility compared with a liquid crystal display, requiring no backlight, higher response speed, and others. What is more, the organic EL display is of a so-called current-controlled type, i.e., the intensity level (gray scale) of light-emitting devices is controllable by the value of a current flowing therethrough, and being the so-called current-controlled type as such is the conspicuous difference from a liquid crystal display of a voltage-controlled type.
As a liquid crystal display, an organic EL display also is classified for driving under two types: direct matrix; and active matrix. An organic EL display of a direct matrix type is simple in configuration, but it has difficulty in implementing a large-sized display with high definition. The development is thus currently active for an organic EL display of the active matrix type. The active matrix type controls a current flow in light-emitting devices in every pixel circuit using active elements, i.e., generally thin-film transistors (TFTs), inside of the pixel circuits, and is described in Patent Documents to 5, i.e., JP-A-2003-255856, JP-A-2003-271095, JP-A-2004-133240, JP-A-2004-029791, and JP-A-2004-093682.